<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style type="text/css">
        span{
            color:green;
        }
        .nav{
            color:red;
        }
        .nav ul li{
            color:blue;
        }
    </style>
</head>
<body>
<div class="nav">
    <ul>
        <li><span>我是什么颜色</span></li>
        <li><span>我是什么颜色</span></li>
        <li><span>我是什么颜色</span></li>
    </ul>
</div>
</body>
</html>